How a sotapanna person experiences the mind?

AN6.97 summarizes the benefits of stream-entry as follows:

AN6.97:1.1: “Mendicants, these are the six benefits of realizing the fruit of stream-entry. What six? You’re bound for the true teaching. You’re not liable to decline. You suffer only for a limited period. You have unshared knowledge. You’ve clearly seen causes and the phenomena that arise from causes.

These benefits accrue because stream-enterers do not have faith in identity view. They have faith in the Buddha, the Teachings and the Sangha. Stream-enterers do not view the world with a mind thinking "this or that is mine". That is unshared knowledge because an everyday layperson habitually considers the world with a mind thinking "this or that is mine".

What is the difference between lay person and a person who achieves sotapannna?

From AN 9.12:

“Again, some person fulfills virtuous behavior but cultivates concentration and wisdom only to a moderate extent. With the utter destruction of three fetters, this person is a seventimes-at-most attainer who, after roaming and wandering on among devas and humans seven times at most, makes an end of suffering. This is the ninth person, passing away with a residue remaining, who is freed from hell, the animal realm, and the sphere of afflicted spirits; freed from the plane of misery, the bad destination, the lower world.

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Does sotapannna person experience less thoughts?would they experience as dukka,happiness, pain like mind state?

Not necessarily less thoughts, more like right thoughts, due to the abandonment of self-view, doubt, and wrong grasp of rules and observances.

The biggest difference is in their actions. Instead of acting impulsively (I want this / I hate this) they think: "will this get me deeper into Samsara or further out of Samsara?" Their every choice is like this.

The second biggest difference is in their vision. Instead of thinking "this thing is so" / "this thing is not so" like the regular people blindly do - stream-enterer thinks "my mind delineates this object and assigns it such and such qualities because I operate within such and such frame of reference".

So whatever happens in their daily life, good or bad, they see it differently and they react differently. They may not do it 100% right (because they are only sotapanna, not Buddha) - but on the overall their mental framework is like this.

The more they act like this, the better they see, and the better they see - the more they act like this. This practice and this teaching improves itself automatically.

This is the reason they are called stream-enterers, because in their own life they have established the self-reinforcing self-perpetuating tendency that inevitably flows towards Nirvana, in maximum of seven lives.

Maybe the simplest answer to this question is that a sotāpanna does experience the mind, whereas most people identify with the mind so strongly that they cannot experience it at all. They are immersed in their thoughts, emotions, and urges, and cannot effectively separate themselves from these mental conditions.

Someone is sotāpanna when they have eliminated the following three obstructions:

• Self-view
• Clinging to rites and rituals
• Skeptical doubt

The first — the elimination of self-view — means that they have abandoned the idea that the self is intrinsically bound to the 'five aggregates': physical forms, feelings or sensations, perceptions, mind structures, and discriminative thinking. All of these still arise in a sotāpanna, but the sotāpanna realizes that these are not identical to him/herself. For instance, imagine a man who feels a sudden wave of hatred towards something. If he is unskilled he merely hates, with no qualifiers; if he has the skills of a sotāpanna he recognizes the hatred as something separate arising within his mind. He may still be controlled by it because his attachments are still strong, but he has created a certain spaciousness — a mental distance from the arising — that he can cultivate with further practice. As he progresses, this spaciousness grows and those arisings weaken.

Sotāpanna is just the first step, and there's no sense expecting the unconscious habits of a lifetime to fall away like dead leaves. So yes, dukkha and tanhā will still be there; the mind will still be filled with thoughts and feelings and urges. We have to get into the water first, and only after that can we start to learn how to swim. But getting into the water is an accomplishment.